Recent technology trends in materials science indicate that the use of nanotechnology-enabled components and materials are gaining more appeal due to the enhanced (and sometimes even breakthrough) performance being exhibited. Functional nanomaterials exhibit many unique and often tunable physical and chemical properties that are different than those of their bulk counterparts. Developments have been recently made towards the fabrication of nanomaterials having well defined shape and dimensions involving either “top down” or “bottom up” fabrication strategies. “Top down” approaches involve cutting down larger structures into the desired shape with the desired dimensions (e.g. nanolithography). “Bottom up” strategies involve growing structures of the desired shape and dimensions from smaller building blocks (e.g. self-assembly). The latter is the preferred approach because it is much more efficient and bypasses the need for cost-intensive and energy-intensive fabrication processes.
Molecular self-assembly is a practical “bottom up” approach to arrive at nanostructured materials. In this approach, self-complementary molecules are designed as ‘building blocks’ with a specific size, shape and at least one functional group, to aggregate in an ordered manner. The resulting ensemble often possesses completely different properties than their smaller building subunits. However, the challenge of this approach is to design the appropriate molecular subunits that can assemble into useful nanostructures in a controlled manner such that the final desired size and shape can be achieved. Consequently, the modular use of hydrogen-bonding molecular building blocks is key to designing novel nanoscale supramolecular structures, non-covalent polymers, organogelators, and liquid crystals, that have useful properties for developing advanced functional materials such as for example adhesives, self-healing coatings, as well as many others.
Amphiphilic alkylated benzoic acid (BA), phthalic acid (PA), and isophthalic acid (ISA) derivatives are known to self-assemble into supramolecular aggregates through hydrogen-bonding either in solution (see, J. Yan, J.-L. Marendaz, S. J. Geib, A. D. Hamilton, Tet. Lett. 1994, 22, 3665-3668), as physio-absorbed monolayers on surfaces (see, S. De Feyter, A. Gesquiere, M. Klapper, K. Mullen, F. C. De Schryver, Nano Lett. 2003, 3, 11, 1485-1488), or in the solid state (see, A. Zafar, J. Yang, S. J. Geib, A. D. Hamilton, Tet. Lett. 1996, 37, 14, 2327-2330). Benzoic acids primarily undergo self-association to form either hydrogen-bonded dimer or catemer motifs (see, J. N. Moorthy, R. Natarajan, P. Mal, P. Venugopalan, J. Am. Chem. Soc. 2002, 124, 6530-6531.) For isophthalic acid derivatives, linear tapes/ribbons and cyclic rosette hydrogen bonding motifs have been observed for different derivatives either deposited on surfaces by STM or in solid state crystal structures (see, Zafar (above), and V. K. Potluri, A. D. Hamilton, J. Supramol. Chem. 2002, 2, 321-326). As described in Potluri (above), the cyclic motif is typically favored with bulkier 5-substituents (i.e., a decyloxy group, or benzhydryloxyundecyloxy), which disrupt the crystalline side-chain packing stabilizing the linear arrangements.
Some exemplary reported benzoic acid and isophthalic acid derivatives incorporate linear alkyl groups with limited lengths (1-20 carbons). Other reported benzoic acid and isophthalic acid derivatives, such as having multiple or branched alkyl chains, are described in Zafar (above), Potluri (above), and S. De Feyter (above). Some alkylated benzoic acid, and isophthalic acid organogelators are also reported. Specific examples of alkylated benzoic acid organogelators include Hong's benzoic acids, for examples, in S. R. Nam, H. Y. Lee, J-I. Hong, Tetrahedron 2008, 64, 10531-10537, and H. Y. Lee, S. R. Nam, J-I. Hong, J. Am. Chem. Soc. 2007, 129, 1040-1041. Specific examples of alkyloxy isophthalic acid organogelators include Hamilton's urea (Potluri, above), 1,2,3-tridecyloxybenzyl functionalized isophthalic acid derivatives (Zafar, above). Also, related alkali salts of alkylated derivatives of aromatic acids as organogelators include, for example, O. Lebel, M-E. Perron, T. Maris, S. F. Zalzal, A. Nanci, J. D. Wuest, Chem. Mater. 2006, 18, 3616-3626, and H-Y. Hu, Y. Yang, J-F. Xiang, C-F. Chen, Chin. J. Chem. 2007, 25, 1389-1393.
The appropriate components and process aspects of each of the foregoing may be selected for the present disclosure in embodiments thereof, and the entire disclosure of the above-mentioned references are totally incorporated herein by reference.
However, there remains a need for new and improved nanotechnology-enabled components and materials, particularly those having self-complementary functional groups which can self-assemble readily by a “bottom up” fabrication strategy to produce well-defined nanostructures and potentially higher-order network structures, that can be useful and desirable properties in developing functional materials.